and Why All Three Types of Tectonic Boundaries are Necessary on a Sphere

4. Describe How Processes in the Interior of the Earth Produce

Plate Tectonics at the Surface

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Plate Tectonics:The Unifying Theory of theSolid Earth

Table of Contents:

2.0 The Unifying Theory of the Solid Earth

2.1 The History Behind the Science

2.11 Early Theories for the Formation of Mountain Belts

2.12 Initial Evidence for Continental Drift and Complications

2.13 WWII and Evidence from the Oceans

2.2 Key Elements of Plate Tectonic Theory

2.21 DivergentPlate Boundaries (Red Sea)

2.22Convergent Plate Boundaries (Cascade Mountains)

2.23 Transform Plate Boundaries (San Andreas Fault)

2.24Modern Evidence for Plate Movement

2.3 Complications to Plate Tectonics Theory

2.31 Mantle Plumes (Hawaii, Yellowstone)

2.4 Driving Mechanisms for Plate Tectonics

2.41 The Earth as a Convective Heat Engine

2.42 Ridge Push and Slab Pull

2.43 Models of the Earth’s Interior

Note: all itemsin the TOC willbe hot links toeach particularsection.

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Plate Tectonics:The Unifying Theory of theSolid Earth

Why Should I Care?

Have you ever wondered:

Why some countries have lots ofnaturalresources, but others have few?

Why California has many earthquakes, but Ohio has very few?

Why the only active volcanoes in the continental US are in the Northwest?

Why most beaches are white sand, but Hawaii has black sand beaches?

Why some Himalayan mountains reach 28,000 ft. in elevation, but the

Appalachian mountains are all less than 7000 ft.?

All of these questions (and more!) can be answered with reference to the theory

of Plate Tectonics. After completing this chapter, you will be able to answer

them yourself!

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Table of Contents

2.0

Plate Tectonics:The Unifying Theory of theSolid Earth

USGS

2.0

Plate Tectonics:The Unifying Theory of theSolid Earth

PlateTectonicsis the first theoryto providea comprehensive viewof theprocesses thatproduced Earth’smajor surface features, includingthecontinents andocean basins.Within the framework of this theory, geologistshave found explanations for the basic

causes and distribution of earthquakes, volcanoes,and mountainbelts. Further, we arenow better able toexplain thedistribution of plants and animals in the geologic past,

as well as the distribution of economically significantmineral deposits.

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Table of Contents

2.0

Plate Tectonics:The Unifying Theory of theSolid Earth

PlateTectonicsis the first theoryto providea comprehensive viewof theprocessesthatproduced Earth’smajor surface features, includingthecontinents andocean basins.Within the framework of this theory, geologistshave found explanations for the basic

causes and distribution of earthquakes, volcanoes,and mountainbelts. Further, we arenow better able toexplain thedistribution of plants and animals in the geologic past,

as well as the distribution of economically significantmineral deposits.

From this image and data from other oceans,oceanographers determined that magnetic stripes ofnormal (colored in the image) and reverse (whitestripes in the image) polarity were bilaterallysymmetrical around a central (red) normal polaritystripe. In addition, after determining the age of thebasalt stripes, they realized the the youngest rockswere along the center stripe, and the rocks got older asone moved perpendicularly away from the centerstripe. Coupled with data that showed elevated heatalong the center stripe, researchers realized that theyhad discovered Wegener’s driving mechanism forContinental Drift!

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Plate Tectonics:The History Behind the Science

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Table of Contents

Evidence from the oceans:

Magnetic Variations in the Seafloor

New ocean floor (crust) was beingcreated at these mid-ocean ridges(central stripes), which then movedaway from the ridge though time.These“seafloor spreading”

zones arethe mechanism by which oceans arecreated/enlarged and by whichcontinents can“drift”apart from eachother!

This will be an interactiveglobe where students canexplore plate boundaries,seafloor ages, areas ofplates, volcanoes,earthquakes, etc.

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Plate Tectonics:The History Behind the Science

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Table of Contents

Evidence from the oceans:

Plate Boundaries

Concept question:

Based on the tectonic boundariesaround North America, why do youthink scientists discarded the term“Continental Drift”?

Text box for students to entertheir thoughts.

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Plate Tectonics:The History Behind the Science

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Evidence from the oceans:

Plate Boundaries

The tectonic boundaries aroundNorth America extend from thePacific margin of California to themiddle of the Atlantic ocean. Thisarea defines a crustal“plate”,which moves as a unit. Since thisunit encompasses both continentalcrust and oceanic crust, we nowcall the theory“Plate Tectonics”instead of Continental Drift.

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Plate Tectonics:The History Behind the Science

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Evidence from the oceans:

Plate Boundaries

Obviously, there is lots more to go with this chapter,but I think this is enough to discuss tomorrow.